DVDs come in various varieties*, for example DVD-R (RW) 4.7GB (4.4GiB). Using these for important data (backed up very week/month) alongside atleast 2 separate Hard Disks (possibly with at least storage medium one off site in case of disaster) can be effective method of ensuring your data is safe.
DVDs can be bought as 'spindles' (which in packs of 100 4.7GB discs can be bought for around $20 USD), which can also act as form of rudimentary storage. DVD Wallets are also available if you want storage with possibly more protection:
Optical discs are much less susceptible to electrical damage, as data is written as physical dents in the structure (it is a form of non-volatile storage) - complex components needed to read the data are not attached to the disc, reducing (integrated) points of failure and in some way making them waterproof.
But they are usually thin and fragile so are easy to break or scratch (and otherwise corrupt the data). Also if kept in poor conditions, the glue holding them together could break down and make them easy to split, or the layers containing the data could be damaged (by oxidation etc). However many DVDs do come with a lifetime warranty, and (more expensive) archive quality discs are available.
Formatting shouldn't be as much of a problem (heavily depending on format - see below*) as along as your DVD and ODD both can use the same standards they should work. HDDs and SSDs (and USB drives, SD cards, etc) require a partition table and filesystem formatting, and support for different formats for varies across systems (e.g. Windows only really supports NTFS and FAT (and exFAT), and possibly BTRFS - it needs more drivers to access other filesystems).
*DVD Formats - They are A LOT of optical disc standards, and you need to bear in mind which format you are getting if you want to maintain compatibility (A DVD Multi with Read Write, Blu-ray, CD functionality may be able to read all of these):
Supported by Panasonic, Toshiba, Apple Computer, Hitachi, NEC, Pioneer, Samsung and Sharp, also supported by the DVD Forum. Should be supported by most DVD-ROM equipment.:
- DVD-R: Can record data only once and then the data becomes permanent on the disc.
- DVD-RW: Read writeable (usually using phase transition), but may have shorter lifespan.
- Also DVD-RAM
Supported by Philips, Sony, Hewlett-Packard, Dell, Ricoh, Yamaha and others. In my experience, some systems may not support them out of the box.
- DVD+R: Can record data only once and then the data becomes permanent on the disc
- DVD+RW: Read writeable (usually using phase transition), but may have shorter lifespan.
Developed by Sony, Samsung, Sharp, Thomson, Hitachi, Matsushita, Pioneer and Philips, Mistubishi and LG Electronics.
- Blu-ray: Not as compatible and more expensive per disc, but can store more data (25GB single layer, 50GB dual layer, other formats can support 100GB+. Data density is a lot higher due to using a smaller blue wavelength. BD-RE discs are read-writable. A similar format called HD DVD was available.
- M-DISC: A hardware variation of DVD or Blu-ray standards that apparently should allow data to be stored for up to 1000 years due to resistance to temperature, humidity, ultraviolet and full-spectrum light etc. However requires a higher powered laser to be recorded too. See also Archival Disc (a similar archive orientated format by Sony and Panasonic designed for the disc to last at least 50 years).
Many of the above formats are also available with more than one layer (e.g. DL (Dual Layer), which are similar but can record more data. However, they are only supported by capable equipment (e.g. DL need Dual Layer support).
These standards vary because of manufacturers implementing there own standards, or by the use of different technologies. Other optical formats can be compared here